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What else can I help you with?
What does the primary key in a data base do?
We know that primary key is the one that is not null and is always unique. A primary key uniquely identifies a record in a table.
How do you Avoid missing column values for non primary key columns?
Use Default and Not NULL
Does primary key allows null value?
No. A primary key requires a value because it is the field that all other values in the row depend on.
Candidate key and primary key differnece?
All Primary keys are definitely Candidate Keys. A Candidate key is one which can be used as a Primary key that is not null and unique. That is one of the candidate keys can be chosen as a primary key.A Candidate key is a Unique Key and it can be used to find out any particular Tuple (row) in a table. The following are the differences between A Candidate key and a Primary Key: 1) A Unique key can be null but not a Primary key 2) On a table we can have only 1 primary key but 'N' number of unique keys.
What is primary key constraint?
Primary Key is a Constraint Used to avoid Duplicate entries in database table and you define primary key the column doesn't allow NULL values.
Can super key have null value?
No they can not
Can a foreign key be null?
yes .a foreign key can have null values
What are the differences between super key primary key candidate key and foreign key?
Super key: A set of attributes that uniquely identifies a tuple in a table. Primary key: A specific super key chosen to uniquely identify each tuple in a table and must be unique and not null. Candidate key: Any super key that could be chosen as the primary key. Foreign key: A field in a table that is a primary key in another table, used to establish a relationship between the two tables.
What is a primary key that is null?
Unique key
What not a likely primary key?
A field that is not unique and null can not be used as a primary key. Praimary key must satisfy the conditions of not null and unique.
Have foreign keys null values?
Yes Foreign key can have null value.
Does primary key allow null?
No
Can a primary key have a blank or null value entered into its cell?
No. A Primary Key is the Unique identifier and cannot be null and cannot be duplicate.
How you create or assign primary key?
A primary key is never null and is also unique . Example of primary key is create table emp (ecode integer NOT NULL PRIMARY KEY);
Can the foreign key accept null?
yes
What are the advantage of primary key?
Primary key that is used to identify a record uniquely. Primary key is a key that always unique and not null. A system generated primary key is called surrogate key.Primary key is the one which is always unique and not null. Advantage of primary key that it helps in identifying a tuple uniquely.
Is alternate key have null value?
An alternate key is a set of one or more attributes that can uniquely identify a record in a database table, similar to a primary key. However, unlike a primary key, an alternate key can accept null values, as its primary purpose is not to enforce uniqueness in the same way. That said, if an alternate key is defined on a column that allows nulls, only one null value can exist in that column to maintain uniqueness among non-null entries.
